Issue with grading and character encoding

[eusebe]

Hello, and thank you for this wonderful extension. I have noticed an issue with character encoding in the messages returned when using the grading feature for exercises. Even though my document is correctly written with UTF-8 encoding, here is how the returned messages appear:

Corresponding source code:

```{webr}
#| exercise: ex_1_r
______(1:10)
```

```{webr}
#| exercise: ex_1_r
#| check: true
if (identical(.result, mean(1:10))) {
  list(correct = TRUE, message = "Bien joué!")
} else {
  list(correct = FALSE, message = "C'est faux, désolé.")
}
```

The only workaround I have found is to write the messages directly using Unicode characters, but this is not very convenient.

Corresponding source code:

Encoding issue:

```{webr}
#| exercise: ex_1_r
______(1:10)
```

```{webr}
#| exercise: ex_1_r
#| check: true
if (identical(.result, mean(1:10))) {
  list(correct = TRUE, message = "Bien joué!")
} else {
  list(correct = FALSE, message = "C'est faux, désolé.")
}
```

Workaround:

```{webr}
#| exercise: ex_2_r
______(1:10)
```

```{webr}
#| exercise: ex_2_r
#| check: true
if (identical(.result, mean(1:10))) {
  list(correct = TRUE, message = "Bien jou\u00e9!")
} else {
  list(correct = FALSE, message = "C'est faux, d\u00e9sol\u00e9.")
}
```